1. Field of the Invention
The invention in general relates to beam forming arrays, and in particular, to apparatus for detecting the signals of the array to reduce side lobe response of the array beam pattern.
2. Background Information
A transducer array has directionality as defined by its beam pattern and when used as a receiver of energy, the arrival direction of the energy may be determined. The beam pattern generally has a direction of maximum sensitivity, or response, which lies along an acoustic axis as well as a plurality of lower intensity responses, known as side lobes, lying along other axes relative to the acoustic axis.
In order to avoid undesired detections of targets or clutter in the side lobes, the output signals of the elements of the array may be weighted, by a process known as shading, to reduce side lobe response. Although shading may significantly reduce the side lobes, they are still present and may still indicate a false target under certain circumstances. In the present invention, the elements of the array are square law detected in a manner to completely eliminate positive side lobes while minimizing any degradation in the main lobe lying along the acoustic axis.